SOURCES AND RESERVOIRS OF TOXOPLASMA-GONDII INFECTION ON 47 SWINE FARMS IN ILLINOIS

Field studies were conducted on 47 swine farms in Illinois during 1992 and 1993 to identify sources and reservoirs of Toxoplasma gondii infe ction. Blood samples were obtained from swine and from trapped wildlif e. Serum antibodies to T. gondii were determined using the modified ag glutination test, incorporating mercaptoethanol. Antibodies to T. gond ii (titer greater than or equal to 25) were found in 97 of 4,252 (2.3% ) finishing pigs, 395 of 2,617 (15.1%) sows, 267 of 391 (68.3%) cats, 126 of 188 (67.0%) raccoons, 7 of 18 (38.9%) skunks, 29 of 128 opossum s (22.7%), 6 of 95 (6.3%) rats, 3 of 61 (4.9%) white-footed mice (Pero myscus sp.), and 26 of 1,243 (2.1%) house mice (Mus musculus). Brains and hearts of rodents trapped on the farm were bioassayed in mice for the presence of T. gondii. Toxoplasma gondii was recovered from tissue s of 7 of 1,502 (0.5%) house mice, 2 of 67 (3.0%) white-footed mice, a nd 1 of 107 (0.9%) rats. Feces of 274 cats trapped on the farms and sa mples of feed, water, and soil were bioassayed in mice for the presenc e of T. gondii oocysts. Toxoplasma gondii was isolated from 2 of 491 ( 0.4%) feed samples, I of 79 (1.3%) soil samples, and 5 of 274 (1.8%) s amples of cat feces. All mammalian species examined were reservoirs of T. gondii infection. All farms had evidence of T. gondii infection ei ther by detection of antibodies in swine or other mammalian species, o r by detection of oocysts, or by recovery from rodents by bioassay. Th e possibility of transmission of T. gondii to swine via consumption of rodents, feed, and soil was confirmed.